My 1st (Indium) ITO Screen Experience

Will update this post as it progresses but won't be bumping it so if you are following just check it once in a while, I am taking my time, having some fun, learning, experimenting and most importantly BEING SAFE.

I have not read all the docs for all Indium compounds but the metal itself is to be treated as HAZARDOUS so please follow forum suggestions for this type of work! Also some of the compounds ARE marked as dangerous, like .1 ppm!

The eventual process will be as described in the PDF I posted here: https://goldrefiningforum.com/phpBB3/viewtopic.php?f=45&t=18370


https://goldrefiningforum.com/phpBB3/download/file.php?mode=view&id=42163

I started with a 50 Ml beaker with 20 Ml ,50% HCL(37%) and added a small corner of the 90x50 MM sheet from the multi-layer LCD screen I am using to test with, about the size of the bottom of the beaker. Also running the same size from a 65 inch TV, batch ITOB

(I will add some pics of both to show the sheeting process of the old screen and the new. And the intermediates)

Let it sit at room temperature for 3 days resulting in a deep yellow liquid with some unidentified particles.

Filtered and added (drop-wise) Ammonium Hydroxide until white platelets began to form,there is also a white colloidal precipitate that is definitely different to the eye.

I am guessing but believe the colloidal form is Tin chloride and the platelets Indium Hydroxide.

Will be testing over the next week....the hydroxide of Indium is easily taken to the sesqui-oxide, In2O3 and if it is Indium Chloride then convert to hydroxide and reduce to same oxide, a vivid yellow powder.

Might as well play with the Tin too but haven't thought it out and encourage a thoughtful process discussion.

Filtrate particles are probably fiber but will test it also.

Maybe we can improve on the process pic? Not my objective , I am just having fun and sharing it with those I believe would appreciate it. I am just having fun!

The process you copied from the pdf is working with ITO targets, in other words, solid chunks of indium tin oxide, not LCD screens.

The SOCl₂ might be quite hard to get, as it is a chemical weapon precursor.

I suggest you try to find articles about recycling LCD:s instead. It will also address the problem with liquid crystals and the toxic nature of the chemicals used inside the screen.

Göran

Thank you for the post, after reading it I realized that "LCD" is probably somewhat misleading although even the article cites 15 % of the ITO market is in LCD manufacture. I've changed the subject line to reflect that.

Not sure I agree with you on what an ITO target is, as I would say anything that contains Indium Tin Oxide would qualify as an ITO target. And that is part of my experiment! I have no wish to deal with messy LCD chemicals and don't recommend it!

Thionyl chloride can be hard to get but if you have legitimate use for it - it can be had last I checked, it can also be made, though every method I've seen are low yielding, it can be made. And part of the experiment is to find a way to accomplish the task (isolate Indium and Tin) without hard to get reagents.

To my knowledge ITO is used as a film deposition so I don't expect to find chunks of it, just a thin film, and that is exactly what I found so far although the material deposition on the 65" screen I mentioned is different in appearance!

When I post the pics it will clarify things I think!

Yeah, I think you need to clarify things. I'm not sure I understand what you are talking about.

An ITO target is the source of the Indium Tin Oxide that is deposited onto a screen in a sputtering deposition machine. It is put down by a process where ionized gas is eroding the target and the molecules that is ripped off from the target is then deposited onto a screen (when making flat panel displays) or other surfaces. The deposited material on the screen is very thin while the target is thick to last for many screens. When a target has lost too much of the ITO it is replaced before the ITO is eroded so much it develops holes. If there is a hole in the ITO target the metal below is starting to erode and contaminate the ITO surface on the screen.

I don't know what screen you are referring to, but ITO is put down on the glass surface of a LCD screen in contact with the liquid crystal material.

There are two other flat screen technologies, plasma (using silver for the conductors) and OLED. I haven't fully researched the process of making OLED displays yet so if that is the display you are talking about then you might know something I don't. But a target is still not a screen.

Göran

Ah, think it is resolved but my ITO target remains the same! The article does appear to be discussing the ITO sputtering target and recovery thereof of the metals AFTER the target is no longer usable while my application of the process is to recover the ITO (thus metals) from the target sputtered eg: LCD Screen.

From what I can see both processes use the HCL leach as described in the PDF but they also discuss H2SO4 leaching. My thought is that the HCL method appears to be the cleanest and economical especially for small scale ops.

I am after the deposited film and in fact have leached a batch from the 90x50 mm screen. The film itself is sputtered onto glass and is leached from it. It is green in this case but upon extraction turns to the Indium oxide color of yellow.

I tried to make this easy to understand as it is my first post of my own attempt to chemically process garbage into $ or to me, FUN!

Will try to be much more explicit in my language and not confuse articles as I obviously did even though the overall process remains the same.

In a sputter coater the target is the source of the metal or substance sputtered while the surface it deposits on is called the substrate. In this case the screen is a substrate, not a target. I think that might be the source of some of the confusion from my side.

Looking forward to hear about your results.

Do you know about any tests for indium in solution? Anything simpler than spectroscopic methods?

Göran

g_axelsson said:

Looking forward to hear about your results.

Do you know about any tests for indium in solution? Anything simpler than spectroscopic methods?

Göran

Click to expand...

Researching that now but the uniqueness of some of its compounds are a good start generally. For example, the hydroxide (white platelets) produced when a salt (in this case chloride) when mixed with Ammonia, produces the hydroxide which upon heating to redness creates the deep yellow Indium Oxide.

The metal itself will alloy with Gallium and Tin to make a room temperature liquid metal (used in modern thermometers).

But will let you know as I dive further into this. Don't recall seeing any in solution test (like Tin Chloride test) either here or in research yet, specific to Indium.

Right now I believe my extraction has separated the black ITO into individual Tin and Indium chloride/hydroxide - hoping to qualify that today.

For those that might be watching this thread, I could not go to sleep tonight without making sure that everyone understands why what g_axelsson chimed in with is VERY important to THIS audience!

While I am just fascinated with the chemistry/process he is looking at this from a refiner/business point of view. The target referred to in the PDF I supplied is the ITO source that is used to apply the ITO coating to the screens / displays that refiners/businesses would be interested in. So the metal count will be down from what's reported in the PDF VS a screen MOST refiners would encounter.

Thanks g_axelsson !

I think the process in the PDF is outstanding especially in conserving user supplied materials and would work equally well for someone with enough to process.

But a small change to avoid harder to get materials could be a good thing for someone.

PS: Just to give an idea of where I am looking at things but certainly not an exhaustive explanation: I've sweated 12 hour catalytic hydrogenation's with Mercury sealed stirrers in a 6 liter round bottom flask.

I'm actually very interested in the topic, not just as a refiner (I'm still at a hobby level) but out of a pure academical interest too. I have been looking into recovering indium from CPU heat spreaders which is the indium source I have easily available. I get a lot of screens too, but I've always turned them in for recycling as I don't want to deal with the liquid crystal chemicals for the tiny amount of indium that is deposited on the screens.

Here is a video where they show an ITO target and also mentions the thickness as "nanometers thick".
https://www.youtube.com/watch?v=4nMuYlSW1Qs

In a paper describing recycling of ITO the thickness is mentioned as 150 nm with 90% indium oxide and 10% tin oxide. An ordinary screen have two layers while a touch screen have two more in the digitizer. Leaching crushed LCD glass recovered 0.25 g indium per kilo of glass.
http://publications.lib.chalmers.se/records/fulltext/165702/165702.pdf
I haven't read the paper yet but it seemed good so I saved it for future reference.

I actually made an initial trial run a couple of years ago. Dissolving the indium from a couple of heat spreaders in HCl and then electroplated it onto a stainless steel cathode. I managed to get about a gram of impure metal back from my first crude experiment. Most ended up in a crude mixture of copper, indium and possibly nickel and partly oxidized powder.
I haven't done any more experiments since then as I'm still trying to read up on the chemistry of indium.

Göran

OK here is an update:
1st to g_axelsson thanks for the links and yes the LCD layer now has to be in the process as will be shown, also I did find a very sensitive test for Indium ions using Quinizarin which can be prepared from:

4 0 g phthalic anhydride and 10 g of pure hydroquinone are heated for 3 hours in a flask in an oil bath at 170-180° C with 200 g pure conc. sulfuric acid and 20 ml of water.


The test was found in -> Spot Tests in Inorganic Analysis By F. Feigl, V. Anger, I will check the library to see if it is listed, if not I will add it. Edited to add link to book as it is not in Library but I can't post there?

Book -> https://books.google.com/books?id=II06Q8GGqNUC&pg=PA248&lpg=PA248&dq=indium+in+solution+color+tests&source=bl&ots=PmPy1vgiFC&sig=ACfU3U2Z1D3_qjEe4gKfwNFHThXioHGZkw&hl=en&sa=X&ved=2ahUKEwi2qeqLqOrkAhUquVkKHeeLB-UQ6AEwGHoECAkQAQ#v=onepage&q=indium%20in%20solution%20color%20tests&f=false

So far, after leaching with HCL and basifying with Ammonium Hydroxide I have white platelets which I have now filtered off to recrystallize leaving me with an opaque solution that I believe is Tin Chloride which I got a positive test for Gold with a Gold test solution. A reverse SnCL2 test

While I am still working with the original materials I've decided to consume the much larger portion of the 90 x 50 mm test LCD screen.

There is in the LCD N-(4-Methoxybenzylidene)-4-Butylaniline but as mentioned in very small amounts (8 microns thick) but I don't want it to interfere with any of the chemistry so this time I will wash the pieces of broken up screen with alcohol (Ever-Clear is fine) - this chemical is heavier than water but not soluble in H2O, so will wash 3 -5 times until clear and then leach as before using the same strength HCL

The N-(4-Methoxybenzylidene)-4-Butylaniline is a yellow liquid so that masked my original observations, this time it won't!

From there we will work up a method to isolate the metals and hopefully calculate yields etc.

Have some pics to post and will do so over the weekend at the latest (running multiple projects right now).

Thanks Rich, I have bookmarked this thread now as it starts to contain a lot of information.

The library section of GRF is a collection of interesting threads, copied, edited and cut down from the original thread on the forum. More or less a collection of the best content. Only moderators can post in the library but if this turns into a good thread about indium recovery and refining it may very well end up there.

Göran

I didn't forget about this, I have some pictures and commentary to add probably over this weekend. To be honest I last posted that I was dumping the entire 90x50 screen into the soup (fresh brew) and I must say that the results so far I can only describe as just a complete mess!

This does not mean it is a loss or not a good process, just totally unexpected!

Hopefully tomorrow I can the pics up!

Just a front and back view of the 90x50 mm LCD board that is the starting material, this until I process the other photos from cell phone.

Front


Back with partially peeled layer

Broken up and thrown into HCL for digestion:


Better pic of the back:

Colored filtrate but had a clear filtered solution that overnight had a white very fine sediment (not shown here yet):



Left in the pot:

Some commentary for thought.

1. Earlier report of positive Gold test with filtered solution used as reagent.

Since I cannot find any reference to SNCL4 reacting the same as SNCL2 I have to assume for the moment that both exist in solution. I know from reading that SNCL6 can also exist in solution so this makes sense to me.

2. Earlier report of light yellow liquid left after filtration and evaporation. Original assumption was that this was from the chemical used in the LCD but today I dissolved it easily in H2O which is more likely the expected SNCL4 which is also a light yellow liquid.

1 & 2 Are from the FIRST nano quick test run on a small quantity of material.

3. I forgot to take a pic but the soup from the entire screen after digestion but before filtration had Blue in the mix but there was a considerable amount of White solid (much more than the Blue) - this needs testing.

4. The filtered solution needs to be processed to make any further determinations. This liquid is water clear with a faint yellow - green tinge.

They have also used Indium-Zinc-Oxide and Indium-Gallium-Zinc-Oxide in some screens so this needs to be taken into account as the workup for next steps are evaluated and performed.

In each case the amount of Indium is in the 90% range.

Just to validate any of the chemistry that evolves here I ordered some ITO sputtered screens with no other contaminants other than glass.

I saw crystals of Indium Chloride or Indium itself falling through solution today....awesome!

Another update:

I do believe that treating the Indium / Tin Chlorides with Ammonium Hydroxide was a good choice maybe as good as the Thionyl Chloride process as the hydroxide of Indium appears to dominate but will try to explain this more scientifically as it progresses.

Found this in my research, note, BLUE :


Suggesting that at room temperature the HCL used did not attack all of the ITO in my experiment, so next step is to find a reasonable temp.

I'm currently running an experiment to leach indium from a P4 heat spreader using weak sulfuric acid. It attacks indium but not tin, so my idea is to selectively dissolve the indium from the CPU and then plate it out (electrowinning) or precipitate it as a hydroxide.

So far it seems to be working, the indium is dissolving but the solder on the other side doesn't seem to be affected the least. It's a bit slow but at higher temperatures and concentrations the sulfuric acid might start to attack the tin and copper.

Just an experiment for fun. 8)

Göran